Passing quoted form from macro to a function

Questions / Help
1

I have been playing with macros lately. Besides the simple examples, this is pretty much the first time.

I tried to pass the “internal” representation of code from a macro to a function in the same module.

Eventually I did it a “clunky” way, but I was amazed at how difficult it was. (Yes, a large part of this is
just my ignorance.)

So: mymac8 can pass code to myfunc – but the first seven tries cannot.

Code below. Any/all insights appreciated.

Hal


###   testme.exs

require MacroPlayground
import MacroPlayground

i = 6
mymac8 i > 5   # This works ok -- versions 1-7 do not 


### MacroPlayground

defmodule MacroPlayground do
  def myfunc(expr) do
    IO.puts "func1: expr inspected = #{inspect expr}"
  end

  defmacro mymac1(expr) do
    IO.puts "mymac1: expr inspected: #{inspect expr}"
    quote do
      IO.puts "mymac1 inside quote: expr inspected = #{inspect expr}"
      MacroPlayground.myfunc(expr)
    end
  end

  defmacro mymac2(expr) do
    IO.puts "mymac2: expr inspected: #{inspect expr}"
    quote do
      IO.puts "mymac2 inside quote: expr inspected = #{inspect expr}"
      MacroPlayground.myfunc(unquote expr)
    end
  end

  defmacro mymac3(expr) do
    IO.puts "mymac3: expr inspected: #{inspect expr}"
    quote do
      e1 = unquote expr
      IO.puts "mymac3 inside quote: e1 inspected = #{inspect e1}"
      MacroPlayground.myfunc(e1)
    end
  end

  defmacro mymac4(expr) do
    IO.puts "mymac4: expr inspected: #{inspect expr}"
    quote do
      e1 = expr
      IO.puts "mymac4 inside quote: e1 inspected = #{inspect e1}"
      MacroPlayground.myfunc(e1)
    end
  end

  defmacro mymac5(expr) do
    IO.puts "mymac5: expr inspected: #{inspect expr}"
    quote bind_quoted: [expr: expr] do
      IO.puts "mymac5 inside quote: expr inspected = #{inspect expr}"
      MacroPlayground.myfunc(expr)
    end
  end

  defmacro mymac6(expr) do
    IO.puts "mymac6: expr inspected: #{inspect expr}"
    quote bind_quoted: [e1: expr] do
      IO.puts "mymac6 inside quote: e1 inspected = #{inspect e1}"
      MacroPlayground.myfunc(e1)
    end
  end

  defmacro mymac7(expr) do
    IO.puts "mymac7: expr inspected: #{inspect expr}"
    e1 = expr
    quote do
      IO.puts "mymac7 inside quote: e1 inspected = #{inspect e1}"
      MacroPlayground.myfunc(e1)
    end
  end

  defmacro mymac8(expr) do
    IO.puts "mymac8: expr inspected: #{inspect expr}"
    e0 = Macro.to_string(expr)
    quote bind_quoted: [e1: e0] do
      e2 = Code.string_to_quoted(e1)
      IO.puts "mymac8 inside quote: e1 inspected = #{inspect e1}"
      IO.puts "mymac8 inside quote: e2 inspected = #{inspect e2}"
      MacroPlayground.myfunc(e2)
    end
  end
end
2

I would think the following comes close to what you are after:

defmodule MacroPlayground do
  def myfunc(expr) do
    IO.puts "func1: expr inspected = #{inspect expr}"
  end

  defmacro mymac1(expr) do
    IO.puts "mymac1: expr inspected: #{inspect expr}"
    MacroPlayground.myfunc(expr)
  end
end

A macro consumes AST and produces AST. Therefore no need to quote inside it if your intent is to pass the AST to the the target function.

3

Thanks very much. It seems obvious now
that you say this.

Almost midnight here, but I will look in the
morning.

Hal